Tandem-operated echo suppressor



July 14, 1925.

H. S. HAMILTON ET AL TANDEM OPERATED ECHO SUPPRESSOB ATTORNEY iil Toremiou'relaiee totronsinissiori circuiis no. more puriziculzwly totreosirussion if we or July i i, iiiilllf i,

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ATE

, NEW jlEIi lEiEii', ASSIGNQES I' I'J JOATEERICAN TELEPHONE ANDTELEGRAPH 2', Al. CillRI-'iliiA/EEQN GI! NEW YURIK.

duplication flied .l'ely 2,

To aii coil-0m may concern:

Be known um: we, HAROLD S. HAMIL- won and Stun-mu iVuiorrr, residing atd East Orange, in the coun'lies like; 1; and items oi New York o ere-eree ociirely, have invented ncrements in Tundei'n llperated nniessors,oi which l'lie following A meat, on.

circuir"; employing echo suppressors,

like of rho oiiieeis of the invention is to an urmingcine wherebytwo orch eo pod with echo supa l a M rod in tandem. The presented when two ormore cirii ire-icing}; an echo suppressor, ore ed together, to preventthe circuits rilaere in; the ends begin to roll: it about w some time,neii eble i1? hear the other The nzilurc of imagine l fli/lilTi Ocircuits, each eonizainir 'iogoci o. boi'ullr, e "voice currentsgenerated will reuse the suppressor near his end to open etc in such e.way as to Sl"i( 1i)-i)lll3l.lll3 "die trimsmission pail, cl'lining;from. die subscriber at the end H, before the voice currents from iiiiecuoscribcr at end Arcaol tlic second suppressor recur lilie end liflliesul iscriber atend l3 already started to tail: and the voice generatedat his steiiou have caused the o nressor near his end to operate, itwill ice eridcnr time the Voice of the suloeerilier .Aik. will iceblocked by the sup- 'ireseor can end while lire s oice of the subscriberin will ice blocked by silie sup-- pressor near the A end 'lollcingunder ti'icse com "'ions would be difi'icull; because por'i; of the meboth subscribers mightbe talking witl'i :ueiiiier one hearing iihcother.

in accordance with the present invention it isprrposcdio overcome iilnsdiliiculty by arranging the colic iressors so that when lg into soon acondiizion that, when two,

subscriber will loc e trouble will be evident an echo euporeseor, ereconneciedi r. lire subscriber at end A begins 1924. semi 1%. 723,796.

such a condition that they maiyiuuciion normally. This control over theecho supderstood from the following detailed, de-

scription when read in connection with the accompanying; drawing,Figure 1. of which iliustiurel'wo iour-wiro repeater circuits uolaptedto be connected together in tandem and provided with echo suppressors ofthe ordinary type, Fig. 2 of which illusirates a similar arrungen'icntprovided with means for rendering, certain of file GClkO suppresssoreinefi'eeiivo in accordance with the pros entinveniion, and F19; 3 ()fWlliCil illus trates a tworwire roll circuit which may loo connected toone of the four-wire circuits without affecting lhc echo suppressors.

Referring 130 Fig. 1, .u four-wire circuit is schematically shown, saidcircuit being equipped with the usual one-way repeaters and :in colicsuppressor between stations X and Y, while a similar circuit isshownbeiween stations Y and Z for terminal connections over eithercircuit. Each individual echo suppressor functionsiu its normal manner,th at is,-wlien transmission takes place "from X to Y the .XY suppressoroperates and short circuits" the opposite branch of the four-wirecircuit, suppressing echoes from Y, and ice verse.

'X -Y end the Y-Z suppressors waves from the party at'Z'should arrive atthe suppressor Z-Y, these waves, would operate the Z Y suppressor, .thuscutting ofi' transmission from X. Furthermore, since the El -Yeuppressor would already be operated the transmission from thesubscriber at Z could noi get through to X and parties at both X ice 'and Z might be talking for some time with out either hearing the other.

Fig. 2 shows schematically an arrangement for obviating this difi icultyby making both suppressor units associated with one of the four-wirecircuits inoperative when the two circuits are connected together intandem. In this figu're, the operators through toll cord circuit isshown at Y between thetwo four-wide circuits. This toll cord is arrangedso that when all four of its plugs are inserted in the. line and networkjacks by which the four-wire circuits are terminated at station Y. theline terminals of the four-wire circuits as well as the networkterminals will be directly connected together. By means of thisconnection it will be app-a rent that an almost perfect condition ofbalance will obtain at each hybrid coil by reason of the fact that thecircuit connected to the'lin'ie jack is identical electrically with thecircuit connected with the network jack.- In short, there is practicallyno unbalance at the Y terminals of either tour-wire circuit so that theeffect is practically the same as though the individual lines of the twofourwire circuits were directly connected together at station Y.

Further details of the apparatus will be clear from a description of theoperation which is as follows: Assume that the lefthand line and netcords at ollicc Y are first connected to the X-Y four-wire circuit, therighthand cords not yet having been connected. Current flt. s from thenegative bat tery A, thropgh relay B,, through the normal contact ofrelay l3, through the simplex connection D derived from the repeatingcoil L thence through the plug and jack terminals to simplex coil Ethrough neutral relay F, and through polar relay G to ground. Relays Bll, and G are operated as shown so that positive battery C, is appliedto the right-hand core simplex D The relay F upon being energized,closes the control wire (which may be a simplex or composite circuit ofany well known type if desired) at one point, but the energization ofthe polar relay G, opens the control Wire at another point so that thecircuit of the relay H at the echo suppressor is not closed andconsequently the two units of the echo suppressor remain in their normalcondition.

The right-hand cords at office Y are then inserted in the Y-Z circuit.Current flows from positive battery G over the contact of relay 13,,through simplex l'). derived from re aeating coil L, over the line plugand jack terminals to simplex E and thence through neutral relay F, andpolar relay G to grormd. This current-is of opposite polarity from thecurrent flowing through the left line cord anc operates the neutralrelay F, but does not peratc the polar relay G Consequently, ground isconnected to the masses Y-Z control wire so that current from battery Jin the echo suppressor flows through and operates the relay H therebyopening the short-circuiting connections controlled by the two units ofthe echo suppressor. The two echo suppressor units associated with theY-Z circuit are. therefore disabled and the built-up circuit is thencomplete with only the XY suppressor functioning.

Consequently. when the subscriber at X talks to the subscriber at Z thevoicecurrents will be transmitted through station Y over the upper linesof each four-wire cir-f cult. Upon arriving at the point Where the echosuppressor XY is applied, said suppressor will be operated toshort-circuit the at this point will be almost perfect as itdoes notdepend upon the simulation of areal line by a network. Therefore, theecho currents which will be returned to station Z Y through the hybridcoil at station Y will be '1 so small in yolumetl-et they garded. Anycomponents of the echo curmay be disrerents transmitted from station Zand which pass through the cord clrcuit to the line transnnttmg "from Yto X will have considerable magnitude but will.

not be permitted to pass to station X by reason of the opera- Ition oithe echo suppressor unit XY.

In case the plugs of the cord at oflice .Y had been inserted in thejacksassociated with the tour-wire circuit extending from cities Y to office75 before being inserted in the jacks associated with the four-wirecircuit extending between otfice X and oflice Y, a circuit would havebeen established from negative battery A through the winding of relayB,. o\ the contact of relay 3,, through the simplex circuit D2, Over theter minals of the plug and jack, through the simplex coil E and throughthe of relays F and G to ground. "In this case, both relays F and Gwould be operated without affecting the control wire to the relay H sothat the echo suppressor units windings associated with the tour-wirecircuit between office Y and office Z would be permitted to functionnormally. Upon inserting the plugs of the cord into the jacks associatedwith the four-wire circuit extending from oflice X to otlice Y a circuitwould be completed from positive battery 0 over' the .front contact ofrelav Ba. over the simplex i in tifieial line ei'mneci-ious.

the eireuit previous imme two wire eireun type, "which is noteqi'iippeii wiih echo suppressors and u'liieh extendsfrom oliice if tosome other office, as .76 If the through eorii shown in Fig. 2%- is usedto connect a toil line of th s r pe with 2; fourwire circuit oi Hie typee'xiemlino; from offi ee X, to oiiiee In the echo. suppressor assoeial'ed wiiih ihe four-Wire circuit will. rei'nuin in operativecondition regmfdiesr-i of whether the connection the four-"wire circuitbe made before or after Hie connection i'o the two-Wire circuit. inestablishing a connec tion from he iwo-wire circuit of Fig. 3 to thefourovire o'ireuii: e'iz'e ulin z; between ofiiee X and oiliee Y of i i2 only the iine portion of the rorrl eireuit will he usecl, theeonneeiions not being established through the umier hail oi the cord iL'CUi'i', to the orfui'timle networks, such l will he connected to thehybrid eoiis in place of eonneeiions to the-nee WOTli fine esiorlieei'eel by swilxzhes shown. I he iine plug of the cord, circuit beinserted! the line jock of the foui"-wire cireuii before theeorreromiiiiiog; plug" inserted in the line iuoi if the iwo-Wire eir-Quit, the echo 5 3' v and Y X will not he 2i.

" "seer units I--i for the reason that i traced will be establishedthrough the relays 13 l and G epei'oting uii three rel vs withoutproducing any-(hung: in the eomroi wire. the other line plug isiTiHi'CiL .er insel'ieel iie ihe jack of the two-wire circuit no controlcircuit will he (IOIIlPiOiGii us 'ihere no simplex eomie0- the jack ofthe two tiou ZLSSOLlHiLfi Wlilli wire ciieuii. iii on The other hand,the line ping of ihe eo ii was i erieei in the jack of the two-wireeireuit bi re ihe EOI'IDQ-CiliOH was esi-zihiisheii in the You eireuii,the opal-mien woohi not he any cl Permit, for the. circuit of reiey ii'u'i'iiilcl not he eompieteci over any smu'ziex LfOUTiLHJL'lQI and housethe eircuii' olreuily i raeeii G would he stublis as before.

The tuniim eomrse" -11 between the two fourmzire circuits shown in i i$3 may be extended from office i0 :inomer office at for reieys B ii endthe left of biz usiizs' another throu h toll cor-d circuit; at Xequipped simili .iy to tiisi; shown. at Y. in this ease the network NWiii be (iiseoimeeteii irom the hybrid eoii at office X and the hyhridsoil. connected to a network jack :iil o manner similar to that shown atoffice Y. Assuming that the conneetiou is built up beginning; at officeZ, the two echo suppressor units YZ and Z- Y will remain connected toihe ioonwire eireuit between oiiiee Y and oii'iee Z for the rea- 7Q sonthat there is no sii'upiei: connection assoeluted with the line jackiii; oi'liCe Z (it being assumed that oifiee 12] is only equipped tomake conneeizions to. a terminal lZ'WOjWiZG) line). When the twoiouroidre cireuits shown are interconnected byiche cord eir euii; atoiiiee Y the connection will be esteblishecl between the eo rcl'ami theflour-wire circuit between ofiice Y and ofliee Ziirst so that the echosup iir-essor units "i --25 and E0 IL-Y will stili remain in theiropemiive eondiiion. Upon establishing (he connetion to the fouewireeire'uib extending from oiiiee Y to office X the echo suppressor iuiitsX-Y and FL-X will be disabled. Upon es- 115 tubiishii ig theconneei'zion at ofiice between these units had already been disabled bythe 5 connection estabiisheel st oiliee if so no change in conditiontakes plate. Upon,

plugging-into the jocks of the fourwvire eir cult amending" to the leftof office A the echo suppressor m'voived at the left of is dis 1% ebiedin a. manner sirtiiiai? to find) iieseiibed in connection Wiilli thefeurmlre'eireuiiz ex tending from ofiiee Y oiiiee Y quently, when theeoinplete oormeeifiioo is es tabiishecl only one poir of echosup'oii'essoi; units will he opera-hive viz, ilie units. Y -Z and Z---Yassociated with the iomwwire eireuit extending from. oiiiee izo oiiieeit will be obvious time the general prioeiples herein iiis'ciosei'l maybe embodied in many other organizations wicieiy (iiiierent from thoseiliustrmbeni Without departiu v from. the spirit of the invenicion asdefirie in. the following claims;

What is ele-io'ied is: l

1. In a transmission system e plurality of transmission circuits ziflapeci. to he-eon-. necked in tandem, a. pair of eeho suppressor unitsassociated with, each cirouiii, one unit llCv being; responsivetoheurrent-s transmitted in one direction. to disable the circuit for'i-lfil'lS-z mission in the opposife il'iIEiGiJiOil and the tandem. torender all of the eel f ressor uni-s u eiieotive e iteeloi xiii mit,$i%ifi$6(i with oiz e fm i T &0

2-. In a transmission system, a plurality of transmission circuitsadapted to be connected in tandem, a pair of echo suppressor unitsassociated With each circuit, one unit being responsive to currentstransmitted in one direction to disable thecircuit for transmission inthe opposite direction and the other unit being responsive to currentstransmitted in the opposite direction for disabling the circuit fortransmission in said first direction, means for connecting saidtransmission circuits in tandem, and circuits con trolled by said meansfor rendering all of the echo suppressor units ineffective except thepair associated with one of said transmission circuits.

3. In a transmission system, a plurality of transmission circuitsadapted to be con.- nected in tandem, a pair of echo suppressor unitsassociatedwith each circuit, one unit being responsive to currentstransmitted in one direction to disable the circuit for transmission inthe opposite direction and the other unit being responsive to currentstransmitted in the opposite direction for dis abling the circuit fortransmission in said first direction, and a cord circuit forinterconnecting a pair of said transmission circuits in tandem, andmeans associated with said cord circuit for rendering the'pair of echosuppressor units associated with one of said transmission circuitsineffective.

4C. In a transmission system, a plurality of transmission circuitsadapted to be connected in tandem, a pair of echo suppressor unitsassociated with each circuit, one unit being responsive to currentstransmitted in one direction to disable the circuit for transmission inthe opposite direction and the other unit being responsive to currentstransmitted in the opposite direction for disabling the ircuit fortransmission in said first direcwhereby the pair of echo suppressoruuits-associated with either of the connected transmission circuits maybe rendered ineffective while leaving the other pair in operativecondition.

5. Ina transmission system, a plurality of transmission circuits adaptedto be connected in tandem. a pair of echo suppressor units associatedwith eaclicircuit, one unit being responsive to currents transmitted inone direction to disable the circuit for transmission in the oppositedirection and the other unit being responsive to currents transmitted inthe opposite direction for disabling the circuit for transmission insaid first direction, a, cord circuit for connecting a pair of said tinsmission circuits in tandem, and controling circuits associated withsaid cord ,circuit for rendering the pair of echo suppressorunits'associated with either of said transmission circuits inoperative,said controlling circuits being so arranged that When the cord circuitis connected to one of said transmission circuits it will not afi'ectthe echo suppressor units associated therewith but when connected to theother transmission circuit the pair of echo suppressor units associatedtherewith Will be rendered ineffective.

In testimony whereof, Wehave signed our names to this specification this1st day of July, 1924.

HAROLD S. HAMILTON. SUMNER l3. WRIGHIY

